Mexicali, Baja California, Mexico

Wastewater System Improvements in Mexicali,Baja California

Status: Completed construction


Untreated wastewater (WW) discharges from the sewage system of city of Mexicali deteriorated the water  quality of  the New River. Due to farmer's opposition to a previous wastewater treatment plant (WWTP) site, alternatives sites were analyzed by the US‐Mexico Binational Committee to build the WWTP. The upgrade of Pump Station No. 4 (PB 4) and construction of the Mexicali II WWTP (first  phase)  to  treat wastewater from the city's northeastern area was required. The WWTP site was located 26 km south of the new Pump Station in an uninhabited area. This project is referred  to as Mexicali II.


The purpose of the Project was to eliminate exposure to untreated WW discharges to the New River by expanding the wastewater treatment capacity, reducing groundwater pollution and the risk of waterborne diseases.


This project consisted of the construction of Las Arenitas WWTP with a  capacity of 20 MGD,  upgrade of PB 4, as well   as construction of 26.4 km force main pipeline and interconnection of major collectors to PB 4 that previously discharged raw WW to agricultural drains.

Project Financing

Total Project Cost US 26.58M
NADB Funding US 10.11M - NADB Grant: BEIF

Project Photos

Results Measurement

Results are measured upon completion of the project through a closeout process that assesses project performance within 6-12 months after completion, as well as the achievement of the goals and objectives established at the time of project certification and financing approval.


Increase access to wastewater treatment services

Reduction of untreated wastewater discharges to water bodies



Increased wastewater treatment capacity

20 MGD

Quantity of uncollected wastewater discharges eliminated

17 MGD



Las Arenitas wastewater treatment plant

20 MGD

48” diameter Force Main (miles)


Upgraded Pump Station (20 MGD)


Significant project contributions

100 % of WW collected is treated. Effluent discharges into a wetland and then ultimately reaches the Rio Hardy.